CN102227660B - Apparatus and method for compensating polarization mode dispersion - Google Patents
Apparatus and method for compensating polarization mode dispersion Download PDFInfo
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
- H04B10/2569—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to polarisation mode dispersion [PMD]
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- G02B6/27—Optical coupling means with polarisation selective and adjusting means
- G02B6/2753—Optical coupling means with polarisation selective and adjusting means characterised by their function or use, i.e. of the complete device
- G02B6/278—Controlling polarisation mode dispersion [PMD], e.g. PMD compensation or emulation
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Abstract
The present invention relates to an apparatus (PMDC) for compensating polarization mode dispersion for an optical transmission fiber (TF) for transmission of optical signals, said optical signals having a first polarization component (x pol) and a orthogonal second polarization component (y pol). The apparatus comprises tuneable means (PCl, DLl, PC2, DL2) adapted to compensating said fiber polarization mode dispersion. The apparatus further comprises a feedback signal generator (FSG) adapted to generating a feedback input signal for said tuneable means (PCl, DLl, PC2, DL2) for polarization mode dispersion compensation. Said feedback signal generator (FSG) comprises polarization means for converting said transmitted optical signal to at least two optical signal components with different defined states of polarization. It has further transforming means for transforming said optical signal components into electrical signal components, wherein each electrical signal component representingone of said defined states of polarization. At least one mixer is earmarked for mixing at least two of said electrical signal components to mixed electrical signals. Means are intended for averaging said electrical signal components to average electrical signals and averaging said mixed electrical signals to average mixed electrical signals. Further means are destined for combining said average electrical signals and said average mixed electrical signals to generate said feedback input signal which is characteristic for a digital group delay of said transmission signal caused by said polarization mode dispersion.
Description
Technical field
The present invention relates to the fiber optics transmission system, and relate more specifically to the equipment and the method that compensate for to the polarization mode dispersion of being introduced when the transmitting optical signal by optical transmission fibers.Light signal has second polarized component of first polarized component and quadrature.
Background technology
In the linear high bit rate long haul transmission system of highly dispersed puppet (for example seabed lightwave transmission system or transcontinental land lightwave transmission system), the interior cross-phase modulation of four wave mixing (IFWM) and channel (IXPM) is the main cause of non-linear punishment (penalty) in the channel.(OOK) compares with on-off keying, uses differential phase keying (DPSK) (DPSK) modulation format can relax these punishment.Also verified, (the RZ)-DPSK that makes zero compares the robustness that correlation between the nonlinear phase shift of the pulse energy of reduction and two adjacent pulses helps the increase of the IFWM of RZ-DPSK with RZ-OOK.
In principle, make polarization bit-by-bit ground in the polarization signal of two quadratures of signal alternately will further reduce non-linear punishment, this is because the FWM between the polarization state of quadrature is very little.Compare with single polarization DPSK thus, by using alternately polarization DPSK (APol-DPSK), can realize the improvement of transmission range.When replacing, DPSK and polarization use the performance strengthened in the optical transmission system that optical nonlinearity reciprocation in the channel wherein is limiting factor.
Along with the bit rate that increases (particularly up to or even greater than 40Gbit/s), polarization mode dispersion (PMD) becomes the physical effect of limit fibre transmission range.
What is worse, PMD is the Statistical Effect that the Mode Coupling by birefringent environmental factor dependence and single mode fibers causes.This means to have certain probability, instantaneous differential group delay (DGD) can be more much higher or much lower than average DGD (being the PMD of optical fiber).
Require emphasis at this, when unacceptable high distortion that the PMD that accumulates on the signal experience transmission range by expectation causes, need a kind of active and adjustable compensation method adaptively to intervene such signal degradation.
Be used for the known feedback-controlled optics PMD compensator (PMDC) that fiber PMD compensates is not suitable for the modulation format (being APol form or quadrature multiplexing form) that uses orthogonal polarization components.
Therefore, there are a kind of needs in the field of this effort, to be used for providing the method and apparatus that the polarization mode dispersion of being introduced by optical transmission fibers is compensated when transmission has the light signal of second polarized component of first polarized component and quadrature.
Summary of the invention
Correspondingly, the invention provides a kind of equipment that the polarization mode dispersion of the light signal after transmission strides across optical transmission fibers is compensated.Light signal has second polarized component of first polarized component and quadrature.This equipment comprises for the tunable devices that polarization mode dispersion is compensated.This equipment further comprises feedback signal generator, and it is used for generating the feedback input signal of tunable devices to be used for the polarization mode dispersion compensation.Feedback signal generator comprises the polarising means that is divided at least two optical signal component with different defined polarization states for the light signal with transmission.In addition, feedback signal generator comprises for the converting means that optical signal component is transformed into electrical signal component, and wherein each electrical signal component is represented a state in the defined polarization state.Additionally, feedback signal generator comprises at least two electrical signal component of electrical signal component being mixed form at least one blender that mixes the signal of telecommunication.In addition, provide and be used for electrical signal component is averaging to form average electrical signal and is used for mixing the device that the signal of telecommunication is averaging to form average mixed signal.In addition, feedback signal generator has for to average electrical signal with average mix the device that the signal of telecommunication makes up to generate feedback input signal, and this feedback input signal is the primary block lag characteristic of the transmission signal that causes by polarization mode dispersion.
The solution that proposes comprises the device that is transformed to electrical signal component for the cross-polarization light signal with transmission, the defined polarization state of each representation in components in the electrical signal component.Detect the power (radio frequency (rf) power particularly) of the signal of telecommunication at each defined polarization state.Do not having under the situation of PMD ideally, this type of polarization state corresponding with the cross-polarization of original input optical signal only taking place.The power (rf power particularly) of one or more other defined polarization state provides information about the polarization degree (DOP) that is caused by fiber PMD with respect to the power of original polarization state.Therefore, by at defined polarization state detected signal power (rf signal power particularly) being made up, make it possible to generate the clear and definite feedback signal of DGD of placing one's entire reliance upon.The device that is used for that signal component is averaging makes can be more much lower than the bit rate of primary signal transmission for the speed of the anabolic process that generates feedback signal.The speed of anabolic process only needs to satisfy the speed requirement of the FEEDBACK CONTROL of PMDC, for example, even it is in also can the scope at 1MHz under high bit rate signal transmission of 40Gb/s.As a result of, the device that is used for average signal is made up to generate feedback signal can operated than under the low speed, and this has reduced equipment cost.According to the present invention, might be by using cross-polarization form (being APol modulation format and quadrature multiplexing form), use independent and with the integrated device of receiver to be used for the polarization mode dispersion compensation of high bit rate (40Gb/s and higher particularly) long haul transmission system (seabed lightwave transmission system particularly).The self-contained unit that is used for the polarization mode dispersion compensation has the advantage that does not need to redesign existing receiver ic.
In a preferred embodiment, using alternately, polarization phase-shifting keying (APol-PSK) comes the light signal of transmission is modulated.This is best solution for the linear high bit rate long haul transmission system of highly dispersed puppet (for example seabed lightwave transmission system or transcontinental land lightwave transmission system).
In another embodiment, polarising means can comprise for light signal that will transmission and converts the polarizer of the optical signal component of following state to: the horizontal/vertical linear polarization state ,+/-45 ° of linear polarization states and a left side/right circular polarization state.
These defined polarization states are very suitable for identifying the primary block that is caused by PMD to postpone.Additionally, can use reliable polarizer such as projection polariscope.Can use the known models such as Stokes' parameter and Poincare sphere simply.
In another embodiment, converting means can comprise for two fast photodiode that optical signal component are transformed into electrical signal component at least.Utilize fast photodiode, can be easily with in addition have 40Gb/s for example or the quicker converting optical signals of high bit rate become and this fast signal bit rate synchronous signal of telecommunication almost.The signal of telecommunication is preferably voltage signal, but it also can be current signal.
Preferably, blender can be suitable at least two electrical signal component are multiplied each other, and mixes the signal of telecommunication to form.Therefore, can before being averaging, carry out the signal of telecommunication multiplying each other fast of electrical signal component.The signal to noise ratio that this has improved the signal to noise ratio of the signal that will be averaging and has also improved feedback signal.
In another embodiment, this equipment can comprise for electrical signal component and the mixing signal of telecommunication are averaging to form average electrical signal and average at least one rf power detector that mixes the signal of telecommunication.In addition, this equipment can comprise at least one AD converter (ADC) that average electrical signal is converted to digital signal.Additionally, this equipment can comprise for the digital signal processor (DSP) that digital signal is made up to generate feedback signal.Utilize the rf power detector, can be easily compare the average signal with much lower bit rate with raw electrical signal to being averaging to generate at output place of photodiode and the quick signal of telecommunication behind blender.By more than, can be easily the bit rate conversion that imports into of for example 40Gb/s be become signal rate in the 1Mb/s scope.As a result of, can use cheap ADC, this ADC can have the sampling rate more much lower than the bit rate of primary light signal.Utilize DSP, can carry out simple computational algorithm to generate feedback signal from the low speed digital signal from ADC.
In alternate embodiments, this equipment can comprise at least one flash-type A/D converter, it is used for electrical signal component and the mixing signal of telecommunication are averaging to form average electrical signal and the average signal of telecommunication that mixes, and converts average electrical signal and the mixing signal of telecommunication to digital signal.In addition, this equipment can comprise digital processing unit (DSP), and it can operate digital signal to be made up to generate feedback signal.
The advantage that this equipment has is by carrying out the reduction of signal rate with the integrated quick AD converter of fast railway and holding circuit.Do not need for example to be similar to rf power detector etc. and be used for attachment device that the signal of telecommunication is averaging.
On the other hand, provide a kind of method that the polarization mode dispersion of being introduced when the transmitting optical signal by optical transmission fibers is compensated.Light signal has second polarized component of first polarized component and quadrature.The inventive method comprises uses feedback process (routine) to compensate according to the polarization mode dispersion of the light signal that transmits to optical transmission fibers.Feedback process comprises that chromatic dispersion compensates to the optical fiber polarisation pattern.In addition, it comprises the feedback input signal that generates for the polarization mode dispersion compensation, and uses feedback signal to regulate the compensation of polarization mode dispersion in the mode of optimizing feedback signal.Generate feedback input signal and comprise that the light signal with transmission converts at least two optical signal component with different defined polarization states to.In addition, it comprises optical signal component is transformed into electrical signal component that wherein each electrical signal component is represented a state in the defined polarization state.Generating feedback input signal further comprises at least two electrical signal component of electrical signal component is mixed to form the mixing signal of telecommunication.It also comprises electrical signal component is averaging to form average electrical signal and is averaging to form the average mixing signal of telecommunication to mixing the signal of telecommunication, and average electrical signal and the average signal of telecommunication that mixes made up to generate feedback signal, this feedback signal is caused, is transmitted the primary block lag characteristic of signal by polarization mode dispersion.
According to another favourable execution mode, can use alternately polarization phase-shifting keying (APol-PSK) that light signal is modulated.
In alternate embodiments, the light signal of transmission can be converted into the optical signal component of following state: the horizontal/vertical linear polarization state ,+/-45 ° of linear polarization states and a left side/right circular polarization state.
In another preferred embodiment, at least two electrical signal component are mixed and can be comprised: at least two electrical signal component be multiply by the formation mixing signal of telecommunication mutually.
Have been found that, for generating the feedback signal can provide about the clear and definite information of DGD, to average electrical signal and average mix the signal of telecommunication make up preferably can comprise to average electrical signal square sue for peace and from this and deduct the average mixing signal of telecommunication.
In another embodiment, can before being combined into feedback signal, average electrical signal and the average mixing signal of telecommunication carry out digitlization to average electrical signal and the average mixing signal of telecommunication.
Description of drawings
In order to understand the present invention better and how to realize the present invention in order understanding, below will only carry out reference to following appended drawings by way of example, wherein:
Fig. 1 schematically illustrates first execution mode of the APol-DPSK transmission equipment of the simplification of using the device that is used for the compensation of feedback optical polarization mode dispersion;
Fig. 2 indicative icon first execution mode of feedback signal generator of the simplification that can in the APol-DPSK of Fig. 1 transmission equipment, use;
Fig. 3 schematically illustrates under the situation of low optical fiber DGD, utilize the polarization state of the light signal that the equipment of Fig. 1 transmits in Poincare sphere;
Fig. 4 schematically illustrates at higher optical fiber DGD and the similar polarization state of Fig. 3;
Fig. 5 schematically illustrates the average distance (FEEDBACK CONTROL that can be used for the PMD compensation) of the polarization state of the optimal polarization state of drawing in the Poincare sphere from Fig. 3 and Fig. 4 to the graphics of input polarization state and optical fiber DGD;
Fig. 6 schematically illustrate can in the APol-DPSK of Fig. 1 transmission equipment, use, with Fig. 2 in second execution mode of the feedback signal generator similarly simplified.
Embodiment
Fig. 1 shows for the optical communication system OCS that replaces polarization differential phase keying (DPSK) (APol-DPSK) transmission.This optical communication system OCS is suitable for seabed light wave transmissions or transcontinental land light wave transmissions.This optical communication system OCS comprises optical transmitter Tx, optical transmission fibers TF, FEEDBACK CONTROL two-stage polarization mode dispersion compensator PDMC and optical receiver Rx.
Transmitter Tx is suitable for generating the APol-DPSK transmission signal with 40Gb/s bit rate.Alternately quadrature TE pattern and the TM pattern of APol-DPSK being transmitted signal exemplarily are depicted as square-wave signal " x pol " and square-wave signal " y pol ".
By means of polarization mode dispersion compensator PDMC, can the polarization mode dispersion (PMD) of optical fiber TF be compensated.The propagation constant of different polarization is depicted as arrow " fast PSP " and " slow PSP ".Propagation constant " fast PSP " is different because of fiber PMD with propagation constant " slow PSP ".Polarization mode dispersion compensator PMDC comprises first order polarization converter PC1, first order delay line DL1, second level polarization converter PC2 and second level delay line DL2.Use polarization to keep optical fiber and realize delay line DL1 and delay line DL2.The output of optical fiber TF is coupled to the input of first order polarization converter PC1.The output of second level delay line DL2 is coupled to receiver Rx via the first optical link OL1.The first optical link OL1 has optical tap OT, and the second optical link OL2 leads to the feedback signal generator FSG of PMDC from here.By means of optical tap OT, approximate 10% signal power outputs to feedback signal generator FSG via second optical link OL2 coupling among the first optical link OL1.
Feedback signal generator FSG is suitable for dividing the generation feedback input signal from the extraction unit of transmission signal.
First execution mode of feedback signal generator FSG is illustrated among Fig. 2, and is appointed as FSG1 in Fig. 2.
Feedback signal generator FSG1 comprises polarizer PO1, polarizer PO2, these three polarizers of polarizer PO3, is converted to the optical signal component with different defined polarization states with the light signal that is used for extracting.
Polarizer PO1 is converted to the light signal that extracts+optical signal component of/-45 ° of linear polarization states.Polarizer PO2 is converted to the horizontal/vertical linear polarization state with light signal, and polarizer PO3 is converted to a left side/right circular polarization state with light signal.
The optics output of each polarizer of polarizer PO1, polarizer PO2 and polarizer PO3 is connected to corresponding fast photodiode FPD1, fast photodiode FPD2 and fast photodiode FPD3.Photodiode FPD1, photodiode FPD2 and photodiode FPD3 are suitable for optical signal component is transformed into electric rf power signal component, and wherein each electrical signal component is represented a state in the defined polarization state.Generally speaking, polarizer PO1, polarizer PO2 and polarizer PO3 and fast photodiode FPD1, fast photodiode FPD2 and fast photodiode FPD3 have similar function, as the quick projection polariscope that is used for cutting out from the optical transmission signals of extracting three state polarizations.In the context of this execution mode, term " fast " means that transformation rate (for example cutting out speed) is bit rate (that is magnitude 40Gb/s), of transmission signal particularly.
The output of photodiode FPD1 is connected to the input of blender M1, the input of blender M3 and the input of rf power detector PD1.The output of photodiode FPD2 is connected to the input of blender M1, the input of blender M2 and the input of rf power detector PD3.The output of photodiode FPD3 is connected to the input of blender M2, the input of blender M3 and the input of rf power detector PD5.The output of blender M1 is connected to the input of rf power detector PD2.The output of blender M2 is connected to the input of rf power detector PD4.The output of blender M3 is connected to the input of rf power detector PD6.
Blender M1 will multiply each other to the corresponding signal of telecommunication that imports into of photodiode FPD3 from photodiode FPD1 to blender M3, to form the electric rf power signal that mixes.It is available to corresponding output place of blender M3 at blender M1 to mix the signal of telecommunication.
Rf power detector PD1 to rf power detector PD6 to being averaging to the mixing signal of telecommunication of blender M3 to the electrical signal component of photodiode FPD3 and from blender M1 from photodiode FPD1, to form corresponding average electrical signal.These average electrical signal are available to corresponding output place of rf power detector PD6 at rf power detector PD1.
Rf power detector PD1 is coupled to the corresponding input of AD converter ADC to the output of rf power detector PD6.ADC converts average electrical signal to corresponding digital signal.
ADC is linked to the digital signal processor DSP for transmission of digital signals.The digital signal of DSP makes up to generate feedback signal, this feedback signal by fiber PMD cause, the primary block of optical transmission signals postpones the DGD characteristic.The output of DSP is connected to feedback signal line FL.
The output of feedback signal maker FSG is connected to the input of the control circuit CE of PMDC via feedback signal line FL.The control input of polarization converter PC1 and polarization converter PC2 is coupled in the signal output of control circuit CE.Therefore polarization converter PC1 and PC2 be by the FEEDBACK CONTROL that depends on feedback input signal, and therefore depend on the degree of DGD.
Fig. 3 and Fig. 4 show signal polarization to the evolution of time, exemplarily as the some Pi in the Poincare sphere.The evolution of signal polarization is drawn to these three photodiode output signals of photodiode FPD3 by photodiode FPD1.
Have been found that for almost there not being PMD the polarization state (SOP) of APol-DPSK transmission signal is shown in the track on the Poincare sphere among Fig. 3 and evolution.Then, the some P of track
iNear centre line C L, centre line C L is all some P
iThe weighting central shaft.Track is to the average distance d of centre line C L
i(by arrow d
iLength describe) very little.
Fig. 4 shows the evolution at the polarization state of higher PMD.In this case, compare average distance d with the situation shown in Fig. 3
iIncrease.
The schematic diagram of Fig. 5 illustrates Poincare sphere middle distance d
iAnd (vertical axes called after " and d
i") depend on the input polarization state (axle called after " be the angle of unit with rad ") of PMDC and optical fiber DGD (axle called after " be the DGD of unit with ps ").Apart from d
iDull decline in low optical fiber DGD zone, this means from fiber PMD than low distortion, and therefore satisfied the demand of feedback signal.For fiber PMD is compensated, suitable feedback process can minimized distance d
iAnd, to be used for minimizing DGD.Below the exemplary feedback process of Chan Shuing can pass through above-mentioned feedback signal generator FSG; FSG1 or the following second execution mode FGS2 (shown in Figure 6) with the feedback signal generator described carry out.Control electronic equipment CE can be fit to first order polarization converter PC1 and second level polarization converter PC2, makes the minimum feedback signal DGD is reduced to ideally zero.
For compensated fiber PMD, can carry out following illustrative methods.
Suppose by transmitter Tx to have produced the APol-DPSK transmission signal with approximate 40Gb/s signal bit rate, and this signal is transferred to polarization mode dispersion compensator PMDC via optical fiber TF.
For feedback process such as following execution that fiber PMD is compensated.
By means of feedback signal generator FSG, from generating feedback input signal through the APol-DPSK of compensation transmission signal.Among the first execution mode FSG1 of feedback signal generator, finish as following shown in figure 2:
Be converted to the optical signal component of following state to what polarizer PO3 will extract through the APol-DPSK transmission signal of compensation by means of polarizer PO1: the horizontal/vertical linear polarization state ,+/-45 ° of linear polarization states and a left side/right circular polarization state.
To fast photodiode FPD3 optical signal component is transformed into electrical signal component by means of fast photodiode FPD1, wherein each electrical signal component is represented a state in the defined polarization state.
By means of blender M1, the electrical signal component of output place of fast photodiode FPD1 and fast photodiode FPD2 is multiplied each other, mix the signal of telecommunication to form first.By means of blender M2, the electrical signal component of fast photodiode FPD2 and output place of fast photodiode FPD3 be multiply by mutually form second and mix the signal of telecommunication.By means of blender M3, the electrical signal component of fast photodiode FPD1 and output place of fast photodiode FPD3 be multiply by mutually form the 3rd and mix the signal of telecommunication.
By means of rf power detector PD1 to rf power detector PD6, fast photodiode FPD1 is averaging to form average electrical signal to the electrical signal component of output place of fast photodiode FPD3, and blender M1 is averaging to form the average mixing signal of telecommunication to the mixing signal of telecommunication of output place of blender M3.
By means of ADC, rf power detector PD1 is carried out digitlization to the average electrical signal of output place of rf power detector PD6 and the average signal of telecommunication that mixes.
For minimized distance d
iBasic idea is maximization expression fast photodiode FPD1 to the output of fast photodiode FPD3, rf power detector PD1, three average electrical output signals of rf power detector PD3 and rf power detector PD5, and minimize rf power detector PD2, three average electrical output signals of rf power detector PD3 and rf power detector PD6, these three average electrical output signals are corresponding to the electrical output signal of blender M3 with blender M1, thereby and corresponding to the product of the electrical output signal of fast photodiode FPD3 with fast photodiode FPD1.Therefore, each square of all average electrical signal sued for peace, and from this and deduct all average mixing signals of telecommunication.Then, this result causes feedback signal.
Below the formula of Jian Huaing has been described above calculating principle:
FS＝Urf1
2+Urf2
2+Urf3
2-Urf1×Urf2-Urf1×Urf3-Urf2×Urf3
Wherein FS is feedback signal.Urf1, Urf2 and Urf3 are the output voltages of output place of rf power detector PD1, rf power detector PD3 and rf power detector PD5.These voltages and fast photodiode FPD1 are proportional to the microwave power (being electrical power) of the output signal of fast photodiode FPD3.Can be by means of blender M1 to blender M3 and rf power detector PD2, rf power detector PD4 and rf power detector PD6 generating item Urf1 * Urf2, Urf1 * Urf3 and Urf2 * Urf3.Generate square Urf1 by means of signal processor
2, square Urf2
2And square Urf3
2Also by means of the signal processor generation with poor.In reality, according to the present invention, before calculating by means of DSP, PD1 carries out digitlization to the output signal of rf power detector PD6 by means of the rf power detector of ADC.
Owing to only measure the rf power level by fast photodiode FPD1 to these three fast photodiode of fast photodiode FPD3, rather than use fast photodiode FPD1 to the fast signal sampling of fast photodiode FPD3, therefore DSP only needs to meet the speed needs of feedback signal, this can be in the scope of 1MHz, rather than in the signal bit rate of approximate 40Gb/s.
By feedback signal generator FSG; FSG1; The feedback input signal that FSG2 generates is transferred to control electronic equipment CE via feedback signal line CL.By means of control electronic equipment CE adaptive first order polarization converter PC1 and second level polarization converter PC2, thus the minimum feedback input signal.
Second execution mode of feedback signal generator FSG is shown in Figure 6, and called after FSG2.The first execution mode FGS1 of the feedback signal generator shown in feedback signal generator FSG2 and Fig. 2 is similar.Those have identical reference marker with the first feedback signal generator FGS1 components identical, and making can be with reference to the explaination of first execution mode about their description.Different with first execution mode, feedback signal generator FSG2 does not have rf power detector PD1 to rf power detector PD6.In contrast, feedback signal generator FSG2 comprises flash-type A/D converter FADC, its be suitable for to from photodiode FPD1 to photodiode FPD3 and blender M1 to blender M3 electrical signal component and mix the signal of telecommunication and be averaging to form on average (mixing) signal of telecommunication, and be suitable for converting average (mixing) signal of telecommunication to digital signal.The same with the ADC of first execution mode, flash-type A/D converter FADC can have lower sampling rate.For example, described FADC has the resolution of several psecs.As example, flash-type A/D converter FADC can be implemented on the substrate with fast railway and holding circuit.Flash-type A/D converter FADC allows among direct survey map 3 and Fig. 4 the time evolution as the polarization signal state shown in the some Pi on the Poincare sphere.Digital signal processor DSP directly calculate then be plotted among Fig. 5 apart from di's and.
For above all execution modes that illustrate, can carry out following modification:
Can only use two or a blender with different performance, rather than blender M1 is to these three blenders of blender M3.
Can use for the device that optical signal component is transformed to the other types of electrical signal component (for example diode array or charge-coupled device (CCD)), rather than photodiode FPD1 is to photodiode FPD3.
Can use be suitable for will transmission light signal convert the device of other types of the optical signal component of the polarization state with different definition rather than polarizer POL1, polarizer POL2 and these three polarizers of polarizer POL3 to.Also can generate more than or be less than three optical signal component.
The present invention also is conducive to be different from the signal bit rate of 40Gbit/s.
Can use the light signal (for example quadrature multiplexing form) of the other types of second polarized component with first polarized component and quadrature, rather than replace polarization APol signal.
The PSK that the present invention also is suitable for other kinds modulates to substitute the APol-DPSK modulation, for example binary phase shift keying (BPSK), Quadrature Phase Shift Keying (QPSK), skew QPSK (OQPSK) ,/4-QPSK and SOQPSK.Can also use make zero (RZ)-(D) PSK and non-return-to-zero (NRZ)-(D) PSK.
PMDC also can utilize more than or be less than two the level realize.In substitute realizing, PMDC can for example realize by single polarization converter and vairable delay line, rather than two polarization converters and first order delay line and second level delay line.
Feedback signal generator FSG; FSG1; FSG2 can be independent devices, rather than is integrated among the PMDC.
Can be with PMDC and/or feedback signal generator FSG; FSG1; FSG2 and receiver Rx integrate.
Claims (13)
1. equipment (PMDC) that compensates in order to the polarization mode dispersion to the optical transmission fibers (TF) that is used for transmitting optical signal, described light signal has the modulation format of second polarized component (y pol) of using first polarized component (x pol) and quadrature, and described equipment comprises:
(PC2 DL2), is suitable for that chromatic dispersion compensates to described optical fiber polarisation pattern to-tunable devices for PC1, DL1;
-feedback signal generator (FSG; FSG1; FSG2), be suitable for generating described tunable devices (PC1, DL1, PC2, feedback input signal DL2) to be being used for the polarization mode dispersion compensation,
Wherein said feedback signal generator (FSG; FSG1; FSG2) comprising:
-polarising means (PO1, PO2 PO3), are used for converting the light signal of transmission to different defined polarization states at least two optical signal component,
-converting means (FPD1, FPD2 FPD3), are used for described optical signal component is transformed into electrical signal component, and wherein each electrical signal component is represented a state in the described defined polarization state,
-at least one blender (M1, M2 M3), are used at least two electrical signal component of described electrical signal component are mixed into the mixing signal of telecommunication,
-be used for to described electrical signal component be averaging to form average electrical signal and to the described mixing signal of telecommunication be averaging to form the average mixing signal of telecommunication device (PD1, PD2, PD3, PD4, PD5, PD6),
-being used for described average electrical signal and the described average mixing signal of telecommunication are made up to generate the device (DSP) of described feedback input signal, described feedback input signal is that the primary block that is caused by described polarization mode dispersion of the light signal of described transmission postpones (DGD) characteristic.
2. equipment as claimed in claim 1, the light signal of wherein said transmission is through polarization phase-shifting keying alternately.
3. equipment as claimed in claim 1, wherein said polarising means comprises polarizer (PO1, PO2, PO3), described polarizer is suitable for the light signal of described transmission is converted to the optical signal component of following state: the horizontal/vertical linear polarization state ,+/-45 ° of linear polarization states and a left side/right circular polarization state.
4. equipment as claimed in claim 1, wherein said converting means comprise that (FPD1, FPD2 FPD3), are used for described optical signal component is transformed into electrical signal component at least two fast photodiode.
5. equipment as claimed in claim 1, (M1, M2 M3) are suitable for described at least two electrical signal component be multiply by mutually and form the described mixing signal of telecommunication wherein said blender.
6. equipment as claimed in claim 1 comprises:
-at least one radio frequency power detector (PD1, PD2, PD3, PD4, PD5 PD6), is used for described electrical signal component and the described mixing signal of telecommunication are averaging to form described average electrical signal and the described average mixing signal of telecommunication,
-at least one analog-digital converter (ADC) is used for converting described average electrical signal to digital signal, and
-digital signal processor (DSP) is used for described digital signal is made up to generate described feedback signal.
7. equipment as claimed in claim 1 comprises:
-at least one flash-type A/D converter (FADC), be suitable for respectively described electrical signal component and the described mixing signal of telecommunication being averaging to form described average electrical signal and the described average mixing signal of telecommunication, and convert described average electrical signal and the described average mixing signal of telecommunication to digital signal, and
-digital signal processor (DSP) is used for described digital signal is made up to generate described feedback signal.
8. method that compensates in order to the polarization mode dispersion to the optical transmission fibers (TF) that is used for transmitting optical signal, described light signal has the modulation format of second polarized component (y pol) of using first polarized component (x pol) and quadrature, and described method comprises:
-use feedback process to compensate according to the described polarization mode dispersion of the light signal that transmits to described optical transmission fibers (TF), wherein said feedback process comprises
-chromatic dispersion compensates to described optical fiber polarisation pattern;
-generation is used for the feedback input signal of described polarization mode dispersion compensation,
-come the described compensation of adaptive described polarization mode dispersion by using described feedback signal, thus optimize described feedback signal,
Wherein generating described feedback input signal comprises:
-convert the light signal of described transmission to different defined polarization states at least two optical signal component,
-described optical signal component is transformed into electrical signal component, wherein each electrical signal component is represented a state in the described defined polarization state,
-at least two electrical signal component in the described electrical signal component are mixed to form the mixing signal of telecommunication,
-described electrical signal component is averaging to form average electrical signal, and the described mixing signal of telecommunication is averaging to form the average mixing signal of telecommunication,
-described average electrical signal and the described average mixing signal of telecommunication are made up to generate feedback signal, described feedback signal is that the primary block that is caused by described polarization mode dispersion of the light signal of described transmission postpones (DGD) characteristic.
9. method as claimed in claim 8, wherein said light signal is through polarization phase-shifting keying alternately.
10. method as claimed in claim 8 wherein converts the light signal of described transmission to the optical signal component of following state: the horizontal/vertical linear polarization state ,+/-45 ° of linear polarization states and a left side/right circular polarization state.
11. method as claimed in claim 8 is wherein mixed described two electrical signal component comprise at least: described at least two electrical signal component be multiply by mutually form the described mixing signal of telecommunication.
12. method as claimed in claim 11 wherein makes up described average electrical signal and the described average mixing signal of telecommunication and comprises: to described average electrical signal square sue for peace and from described and deduct the described average mixing signal of telecommunication.
13. method as claimed in claim 11 was wherein carried out digitlization to described average electrical signal and the described average mixing signal of telecommunication before described average electrical signal and the described average mixing signal of telecommunication are made up to form described feedback signal.
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| PCT/IB2008/055659 WO2010061247A1 (en) | 2008-11-28 | 2008-11-28 | Apparatus and method for compensating polarization mode dispersion |
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| US (1) | US8494373B2 (en) |
| JP (1) | JP2012510747A (en) |
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| US9692549B2 (en) * | 2011-06-29 | 2017-06-27 | Spatial Digital Systems, Inc. | Accessing CP channels with LP terminals via wavefront multiplexing |
| CN103023570B (en) * | 2011-09-26 | 2016-03-30 | 富士通株式会社 | Nonlinear compensating device, method and transmitter |
| CN102725977B (en) | 2011-12-01 | 2014-07-09 | 华为技术有限公司 | A kind of optical signal compensation device |
| CN102681287B (en) * | 2012-05-18 | 2014-11-12 | 上海交通大学 | Full optical code type conversion system based on stimulated Brillouin scattering effect |
| US9419711B2 (en) * | 2012-09-17 | 2016-08-16 | Ofs Fitel, Llc | Measuring in-band optical signal-to-noise ratio (OSNR) |
| CN103267481B (en) * | 2013-05-28 | 2016-01-27 | 哈尔滨工业大学 | A kind of pick-up unit of polarization maintaining optical fibre polarization axle and apply the method that this device detects polarization maintaining optical fibre polarization axle orientation |
| US9673899B2 (en) * | 2013-10-22 | 2017-06-06 | Exfo Inc. | In-band OSNR measurement on polarization-multiplexed signals |
| WO2016046315A1 (en) * | 2014-09-24 | 2016-03-31 | Danmarks Tekniske Universitet | System for transmitting and receiving multi-polarized signals |
| CN106656314B (en) * | 2015-10-31 | 2019-05-24 | 华为技术有限公司 | A kind of method and device monitoring optical communication network dispersion |
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| CN102227660A (en) | 2011-10-26 |
| US8494373B2 (en) | 2013-07-23 |
| JP2012510747A (en) | 2012-05-10 |
| US20110229143A1 (en) | 2011-09-22 |
| WO2010061247A1 (en) | 2010-06-03 |
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